Potjeth to each



UNITED STATES PATENT OFFICE.

THOMAS C. CLARK, OF OAKLAND, ASSIGNOR TO JAMES STRATTON, OF SAME PLACE, AND RICHARD E. COADY, OF ALAMEDA, CALIFORNIA, ONE- FOURTH TO EACH.

EXTRACTING PRECIOUS METALS FROM ORES.

SPECIFICATION forming part of Letters Patent No. 229,586, dated July 6, 1880.

Application filed December 27, 1879.

To all whom it may concern:

Be it known that I, THOMAS C. CLARK, of Oakland, county of Alameda, and State of California, have invented an Improvement in Extracting Precious Metals from Ores; and I hereby declare the following to be a full, clear, and exact description thereof.

The object of my invention is to perform the disintegration and desulphurization of ores so to as to bring the said ore into proper condition for easy pulverization and the precious metals contained therein into a suitable form for a1nalgamation by freeing them from the union and influence of baser metals. In order to accomplish this object the ore is crushed into pieces about the'size of ordinary Indian corn. That portion containing sulphurets generally becomes finer, since it is more friable. The object of crushing it to this size is to prevent loss of gold and to facilitate washing operations.

The ore, after being crushed as described, is placedin an ordinary roasting-furnace. After being roasted for a suitable length of time the heat is raised, so the sulphur will burn freely, after which the heat is let down again, a free supply of oxygen being furnished during the whole process of roasting.

After the ore has become-dead and lies like sand in the furnace, and no more scintillation is apparent, itis heated up to a good red heat, but not made too hot.

In a suitable receptacle beside the furnace I form a cold bath, into which the ore is drawn 5 While in its heated condition fresh from the furnace. This bath is formed of a solution of salt, prussiate of potash, and caustic soda or caustic potash.

For one ton of gold ore containing five per 40 cent. or less of sulphurets I form my bath in about the following proportions: I take about thirty gallons of cold water, to which common saltis added until a saturated solution is formed.

I then dissolve one pound of prussiate of potash in water and ponrit into the solution, and 5 also dissolve one pound of caustic soda in water and add it to the solution. The bath then contains chloride of sodium, prussiate of potash, and caustic soda. For the latter caustic potash may be substituted with a like re 0 sult.

The red-hot ore being drawn into the cold solution described, a complete desulphurization is effected, as well as a disintegration.

Where there is a higher percentage of sul- 5 phur in the ore additional quantities of the prussiate of potash and caustic soda are added, the proportions of the solution being thus altered to suit the requirements of the class of ore under treatment. The proportions may also be modified for ore of different character.

I am aware that ore has frequently been roasted and dumped while red hot into cold water or into cold solutions, and I therefore do not claim, broadly, such process; but

What I do claim as new, and desire to secure by Letters Patent, is-

The process of disintegrating and desulphurizing ores and freeing the precious metals therein contained, consisting in first roasting the ore to a red heat, and while in that condition placing it in a cold bath composed of a solution'of salt, prussiate of potash, and caustic soda or caustic potash, in about the proportions named, substantially as herein described.

In witness whereof I have hereunto set my hand.

THOMAS C. CLARK.

Witnesses:

GHAs. G. YALE, S. H. NoURsE. 

